Implement professional error handling and user feedback system

Major UX Improvements:
- Replace all alert() dialogs with elegant toast notifications
- Add comprehensive loading states for all async operations
- Implement client-side form validation with visual feedback
- Add React Error Boundary for graceful error recovery

Components Added:
- Toast notification system with success/error/warning/info types
- useToast hook for easy notification management
- ErrorBoundary component with development error details
- Form validation with real-time feedback

User Experience:
- Professional toast notifications instead of browser alerts
- Loading indicators prevent double-clicks and show progress
- Immediate validation feedback prevents submission errors
- Graceful error recovery with retry options
- Enhanced accessibility with proper ARIA labels

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

lib/useToast.ts

@@ -0,0 +1,63 @@
+'use client';
+
+import { useState, useCallback } from 'react';
+import { Toast, ToastType } from '@/components/Toast';
+
+export function useToast() {
+  const [toasts, setToasts] = useState<Toast[]>([]);
+
+  const addToast = useCallback((
+    type: ToastType,
+    title: string,
+    message?: string,
+    duration?: number
+  ) => {
+    const id = Math.random().toString(36).substr(2, 9);
+    const toast: Toast = {
+      id,
+      type,
+      title,
+      message,
+      duration: duration ?? (type === 'error' ? 7000 : 5000), // Errors stay longer
+    };
+
+    setToasts((prev) => [...prev, toast]);
+    return id;
+  }, []);
+
+  const removeToast = useCallback((id: string) => {
+    setToasts((prev) => prev.filter((toast) => toast.id !== id));
+  }, []);
+
+  const clearAllToasts = useCallback(() => {
+    setToasts([]);
+  }, []);
+
+  // Convenience methods
+  const showSuccess = useCallback((title: string, message?: string) => {
+    return addToast('success', title, message);
+  }, [addToast]);
+
+  const showError = useCallback((title: string, message?: string) => {
+    return addToast('error', title, message);
+  }, [addToast]);
+
+  const showWarning = useCallback((title: string, message?: string) => {
+    return addToast('warning', title, message);
+  }, [addToast]);
+
+  const showInfo = useCallback((title: string, message?: string) => {
+    return addToast('info', title, message);
+  }, [addToast]);
+
+  return {
+    toasts,
+    addToast,
+    removeToast,
+    clearAllToasts,
+    showSuccess,
+    showError,
+    showWarning,
+    showInfo,
+  };
+}